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Finding the Fourth Proportional to 431.30, 643.23 and 389.78

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Solution

The fourth proportional to 431.30, 643.23 and 389.78 is: 581.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.30 : 643.23 = 389.78 : x
  2. Step 2: Convert to fraction form
    431.30/643.23 = 389.78/x
  3. Step 3: Cross multiply
    431.30x = 643.23 × 389.78
  4. Step 4: Simplify right side
    431.30x = 250,714.97
  5. Step 5: Solve for x
    x = 250,714.97/431.30
  6. Step 6: Final answer
    x = 581.31

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.